Impulse correcting repeater



ly 1949. c. GILLINGS' ET AL 2,475,546

IMPULSE CORRECTING REPEATER I Filed Dec. 8, 1944 E53 ARZ F4\V-P-O\ ---T I 1 1 mm 1 43 i i a I I IN VENTORS CHARLES GILLINGS CHARLES E. BEALE ATTORNEY Patented July 5, 1949 STATES PATENT OFF-ICE IMPULSE oon ifs friiiio REP-EATER Cha les i li and arles Edmund. Bea e,

LiVe TDDPL E l nd i nnrs to Au a c Electric Laborateries Inc., Chicago, Ill, a corporation of Delaware A l c ti c er 8, 1944,, seria 567,22 InGreat Britain February 19, 1944 9 Claims.

1 The Pre e inv nti e tes t e h n litre signallingsystems and is more particularly appli ab t te phon ys s employing ic frequency dialling arrangements for the setting up of automatic telephone switching apparatus ever. long trunk lines. The inuention is moreover particularly concerned with systems in which the responding apparatus is of the type which is operated by direct current impulse trains into the reeeived voice frequency impulse trains are converted at. the incoming end of the Voice re uen y S n l n l n In such systems the impulse accepting relays of the selectors at the receiving end of a voice frequency trunk line are controlled over the line elephone or l k syst ms rra em is proonducto s tha i an cur ent su es which are produced particularly at each opening of the direct current circuits to these inductive relays, are allowed to feed bacl; on to the voice frequency trunk line, they may cause the line echo sup- P SQI b ntarily s t h d over to th opposite direction thus causing mutilation of further incoming voice frequency signals. The chief surges-to be guarded against are those produced during each impulse train and those produced when switching through from one selector switch to another, and it is the chief object of the present invention to provide means for preventing these surges from becoming effective on the voice frequency trunk line echo suppressors.

According to one feature of the invention, in telephone or like systems an arrangement is providd for converting trains of voice frequency impulses into interruptions in a direct current cireuit suitable for effecting the operation of an automatic switch in which the first impulse of each train is employed to effect the disabling of the transmission path between voice frequency input and direct current output and is not directly repeated to the outgoing circuit.

Aecording to another featureof the invention, in telephone or like systems an arrangement is provided for converting trains of voice frequency impulses into interruptions in a direct current circuit suitable for effecting the operation of an automatic switch in which in response to the first impulse of a train the transmission path between voice frequency input and direct current output is disabled and this impulse is prevented from producing a corresponding interruption of the direct current circuit sueh as are produced by succeeding impulses if any and an additional interruption is produced at the end of the train of impulses.

A further feature of the invention is that in vided o con erting t in f voice reque cy pulses. into interruptionsin a direct current circuit suitable for effecting the operation of an automatic switch in which in response to. each train of impulses the transmissionpath between voice frequency input and direct current output is disabled throughout the train of impulses and for a sufiicient period thereafter to enable the switch which responds to the impulses to perform a hunting operation and switch through to a succeed ne wit h- The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the acjcompar ying drawing which shows part of the circuit of a typical incoming VF/DC relay set as modified for the purpose of carrying out the invention. r

In the proposed method the first impulse of each received impulse train is absorbed but serves to disable the transmission path between the input and output sides of the circuit. At the end of each output D. C. train a locally generated impulse of compromise ratio value is added to replace the one whichwas absorbed. The disabling of the transmission path is subsequently maintained'for a further period sufficient to allow the selector switch in question to perform its hunting operation and to switch through to a receiver being connected across these leads in usual manner. Leads t2 and I3 connect up with the incoming selector switch, the impulse accepting relay A of which is shown. The selector switch to which leads l2 and [3' connect may be any of the standard Strowger-type selector switches and for illustration purposes, of the type shown in Figure 2 in the patent to Sanders, 1,868,994, issued July 26, 1932. Relays 221, 22-2, and 223 of the Sanders patent correspond respectively to the A, B, and C relays referred to herein.

In response, to a 'V, F; seizing signal of X frequency; contacts X are closed, and, relay L is operated responsive to the completion of its operatingcircuit by the contacts X in the V. F. receiver and at ccntacts LI and L2 introduces the combined lqss pad comprising resistances YAYET into the speech transmission circuit. The X contacts are attached to a relay operated responsive to receipt of, the X frequency seizing signal and will remain operated until such time as the final clear down signal is subsequently transmitted by the distant outgoing operator to release the X relay. Relay NR is also operated and at its contacts NR2 prepares the selector switch for receiving a train of impulses by extending the earthed relay IL forward over the negative lead to operate the selector A relay on its upper winding. Any surge which may be produced during the energisation of relay A will not do any harm, since by the time V. F. impulse trains are transmitted forward from the distant end of the V. F. trunk line the selector A relay will be steadily operated and no surge currents will be present on the line. Relay AR is also operated on the seizure of the unit and at contacts ARI prevents the operation of relay EB by contacts NRI.

In response to a received train of V. F. impulses relay AR is impulsed responsive to impulses of Z frequency and on its first release brings uprelay EB. Contacts ARZ are ineflective to open the circuit to relay A at this time, the loop being maintained closed over contacts C3, normally closed contacts controlled by contacts Cd, NR2 and EMZ. In this manner the first impulse is absorbed in the circuit. Relay EB in operating at contacts EBI prepares a circuit for relay EM (at present short-circuited) and at EB2 brings up relay SG. Relay SG in operating at contacts SGI prepares a circuit to relay and at SG2 disconnects the speech transmission path. On the subsequent re-energisation of relay AR, contacts ARI short-circuit relay EB which commences to release slowly and during this time a circuit is completed over contacts EBI for relay EM. Relay EM in operating at contacts EMI brings up relay 0 and at contacts EMZ disconmeets the original seizing circuit for relay A, a circuit being, however, maintained owing to the operated condition of contacts EB3 and ARZ. Relay C in operating at contacts Cl short-circuits one of its windings to render itself slow to release, at contacts 02 maintains an alternative holding circuit for relay SG, at contacts C3 further disconnects the speech transmission circuit and at contacts 04 replaces the forward holding earth to relay A by a holding loop in readiness for the transmission of loop impulses to this relay.

Relays EB and EM are so interconnected that relay EB is energised on each break of relay AR and is short-circuited on each make, while relay EM is energised on each make of relay AR and is short-circuited on each break. Assuming a range of impulse speeds of 7-12 impulses per second with a nominal break-to-make ratio of 2-1, the break periods will vary from 56 milliseconds (m. s.) at 12 I. P. S. to 96 m. s. at '7 I. P. S. and the make periods will vary from 28 m. s. to 48 m. s. For reasons which will be appreciated better as the description proceeds relays EB and EM are designed to release under short-circuit conditions after periods of 50-75 m. s. and 60-90 m. s. re-

spectively.

Relay EB will therefore hold even if the first make period of relay AR has the maximum value of 48 m. s. and hence when relay AR. releases to initiate the second break period, relay EB will remain held while relay EM will be short-circuited over contacts ARI and EBI. At the same time contacts AR2 initiate the first output break period to the selector A relay. If the break period delivered from relay AR is unduly long, i. e. of the order of 90 m. s., relay EM may release during this time and in so doing it would '4 open the circuit of relay C which would hold operated for a further interval due to its short circuited winding, while at contacts EM2 it would terminate the first output break period to the selector A relay.

On the second make period delivered from relay AR relay EB is again short-circuited, while relay EM is re-operated if it has released or is maintained if it has remained held during the preceding break period. If relay EM has failed to relase during the preceding break period contacts ARZ in reclosing terminate the first output break period to the selector A relay.

Similar remarks apply to subsequent break and make pulses delivered from relay AR so that if the digit 5 has been dialled, at the end of the train of received V. F. impulses the selector A relay will have received four impulses. At this time relay AR will remain steadily operated until the next train of V. F. impulses is received and hence relay E-B will release after its release lag of 50-75 m. s., and in so doing at contacts EB3 initiates the fifth output break period to relay A, while at contacts EBI relay EM is short-circuited and commences to release.

When relay EM releases after its slow release period of 60-90 m. s., contacts EM l cause relay C to commence to release slowly and contacts Ell I2 terminate the fifth output break period to relay A. In the selector referred to previously herein, relays A and B will then remain held while the selector relay 0 will commence to release slowly. After the release lag of this relay, which is usually of the order of m. s., the selector wipers will be cut in on the level to which they have been raised and searching will take place for a free outlet to a succeeding selector.

During this time relay 0 in the incoming relay set (which has a similar release lag to the selector C relay) will release and will open the circuit to relay SG which commences to release slowly. The release lag of relay SG is such as to ensure sufficient time for the selector to find a free outlet in the level selected and to switch the line through to the A relay of a subsequent selector.

Similar remarks apply to subsequent trains of impulses and it will be seen that any surges produced by the selector impulsing relays during dialling or during switching through are prevented from extending back to the V. F. trunk line.

In the case where digit l is received, relay AR in releasing will bring up relays EB and SG in the usual manner. On the re-operation of relay AR relay EB will commence to release slowly while relays EM and C are operated. When relay EB releases relay EM commences to release slowly and contacts EB3 initiate the output break. Subsequently when relay EM releases, this break period is terminated by contacts EMZ and relays C and SG commence to release slowly in turn in the usual manner.

It should be mentioned that the release lag of relay EB is made a minimum of 50 m. s. so as to ensure that it will remain held during dialling at all the speeds contemplated while it is made a maximum of 75 m. s. so as to ensure that the value of the output make period preceding the locally generated output break period at the end of each train is not long enough to release the selector 0 relay. Relay EM has a minimum release lag of 60 m. s. to ensure that the selector A relay concerned receives satisfactory break periods while the release lag of relay EM is made a maximum of 90 m. s. to ensure that no output break period to relay A shall exceed this value since otherwise the selector B relay concerned might fail to hold.

The I relay serves at its contacts Ii in known manner responsive to battery reversal in the line circuit when the called party answers to disconnect resistance YC from across the lines and at its contacts I2 releases relay L. Relay L, at its contacts L1 and L2 short-circuits the series resistances YA, YB and YD, YE.

What we claim as new and desire to secure by Letters Patent is:

1. In a telephone system, a repeater, an incoming line over which a train of voice frequency signals are received and an outgoing line connected to said repeater, said repeater at times associating said lines to permit the transmission of speech signals therebetween, means in said repeater reponsive to the first impulse in said train of voice frequency impulses received over said incoming line for disassociating said lines to prevent speech transmission and for absorbing the first impulse, and means in said repeater responsive only to impulses succeeding the first impulse in the train for repeating corresponding direct current impulses over said outgoing line.

2. In a telephone system, a repeater, incoming and outgoing lines connected to said repeater, said repeater at times associating said lines to permit the transmission of speech signals therebetween, a seizing signal and a train of voice frequency impulses received over said incoming line, means in said repeater operated responsive to said seizing signal to include a loss pad in said speech transmission circuit, means in said repeater responsive to the first impulse in said train of voice frequency impulses received over said incoming line for disassociating said lines to prevent speech transmission, means in said repeater reponsive only to impulses succeeding the first impulse in the train for repeating corresponding direct current impulses over said outgoing line, and means in said repeater responsive to the termination of the train of impulses for reassociating said lines after a predetermined time interval.

3. In a telephone system, a repeater, incoming and outgoing lines connected to said repeater, said repeater at times associating said lines to permit the transmission of speech signals therebetween, means in said repeater responsive to the first impulse in a train of voice frequency impulses received over said incoming line for disassociating said lines to prevent speech transmission, means in said repeater responsive only to impulses succeeding the first impulse in the train for repeating corresponding direct current impulses over said outgoing line, said first means responsive to the termination of the train of impulses for reassociating said lines after a predetermined time interval.

4. In a telephone system, a repeater, an incoming line over which voice frequency signals of various frequency values are received and an outgoing line connected to said repeater, said repeater at times associating said lines to permit the transmission of speech signals therebetween, means in said repeater responsive to a frequency of one of said values to prepare the repeater for operation, means in said repeater responsive to the first impulse in a train of impulses of a voice frequency of another of said values received over said incoming line for disassociating said lines to prevent speech transmission, means in said repeater responsive to the succeeding impulses of the train for repeating corresponding direct current impulses over said outgoing line, and means in said repeater responsive to the termination of the train of voice frequency impulses for transmitting an additional direct current impulse over said outgoing line and subsequently reassociating said lines.

5. A telephone system as claimed in claim 4 wherein the duration of the additional direct current impulse transmitted by said last means is independent of the duration of the impulses in said train of voice frequency impulses.

6. A telephone system as claimed in claim 2 wherein said third means is operative to exert a correcting effect on the direct current impulses repeated thereby when the received voice frequency impulses are seriously distorted.

'7. In a telephone system as claimed in claim 3, a terminating impedance connected across said incoming line, said first means disassociating said lines to prevent speech transmission by opening said incoming line While leaving said terminating impedance connected thereacross.

8. In a telephone system, a repeater, an incoming line over which voice frequency impulses are received and an outgoing line connected to said repeater, means in said repeater responsive to a train of said voice frequency impulses received over said incoming line for repeating direct current impulses over said outgoing line, means whereby each of the repeated impulses corresponds to one of the received impulses succeeding the first received impulse in the train, said first mentioned means being operative to exert a correcting effect on the direct current impulses repeated thereby when the voice frequency impulses are seriously distorted, and means in said repeater responsive to the termination of the train of voice frequency impulses for transmitting an additional direct current impulse over said outgoing line.

9. In a telephone system, a repeater, an incoming line over which voice frequency impulses are received and an outgoing line connected to said repeater, means in said repeater responsive to a train of said impulses received over said incoming line for repeating impulses over said outgoing line, means whereby each of the repeated impulses corresponds to one of the received impulses succeeding the first received impulse in the train, said first mentioned means being operative to exert a correcting effect on the impulses repeated thereby when the received impulses are seriously distorted, and means in said repeater responsive to the termination of the train of received impulses for transmitting an additional impulse over said outgoing line.

CHARLES GILLINGS. CHARLES EDMUND BEALE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,606,199 Wilbur Nov. 9, 1926 1,829,803 Korn Nov. 3, 1931 2,153,654 Trechcinski Apr. 11, 1939 2,301,523 Clay et al Nov. 10, 1942! FOREIGN PATENTS Number Country Date 559,016 Great Britain Feb. 1, .1944 

